The ‘Oi No Ka ‘Oi Steel Guitars - Part IV

December 23, 2022 • Kevin Gillies • Instruments and Luthiers

Ed note: Kevin Gillies is Sole Proprietor and Luthier at ‘Oi Acoustics. He is a residential architect, land use planner, woodworker, and luthier. In his words, he "strives to achieve elegance through simplicity, reducing the number of visual elements to the minimum required. The focus is on ergonomics and tone to make an instrument that speaks for itself and you won't want to put down." This multi-part series delves into Kevin's design philosophy and what he considers important elements when it comes to instrument architecting and selection. This is Part IV of a multi-part series. © 2022 www.oiacoustics.com.

PART IV: THE SIGNAL CHAIN

To date we've looked at some of the components in designing the steel guitar, including how strings work. The rest of the electronic signal chain includes the headstock with tuning machines and nut; body construction; the tail with saddle and string anchor; and electronics with pickup, controls, cord, amp and speaker. Although they are discussed as distinct entities, they need to be matched as well as possible as all are part of a chain in which a weak link can counteract everything else.

Fundamentally, we don't want to lose any string energy due to heat loss through soft materials or deflection. Strings must be anchored with as little horizontal movement as possible to transfer as much energy to the pickup as possible, and not bleed off into the body or poorly fitting parts.

THE HEADSTOCK

Tuning Machines: The most important factor with tuning machines is to have a rigid post. One that deflects is a great way for poor tuning capability, slippage and energy loss. I now exclusively use Gotoh tuners as others just haven't been worth it for me, although there are good alternatives out there, and they are made to order for me in a really nice Cosmo Black color.

Machine Angle: My reference point is acoustic guitars, but having a standard peghead, designed for a vertical guitar, isn't ergonomically friendly on a horizontal steel. My headstock design was based on an upside down version of the traditional slotted classical guitar peghead which used posts that anchored on both sides of the slot to minimize deflection. In order to use modern tuners, I modified this idea to use stepped sides to maintain perpendicular tension on the tuner post, leaving a minimum of ½" of stock between slots in order to inlay a carbon fiber bar for structural support. Strings which are exactly straight through is theoretically superior, but impossible with a wood headstock as the center mass is critical to the structure. It was only after designing it that I saw the same approach in most pedal steels.

String Angle: Downward force of about 35 degrees from the strings to the nut is necessary to maintain solid contact. Note that in this design, the headstock is not tilted downward as with a regular guitar, as that creates a week point due to either short grain or a scarf joint. The passive section of the string between the tuning machine and nut is not well understood. What is known is that if the section is very short, it inhibits accurate tuning in that short stiff string sections are much more sensitive to tune. A longer passive section allows for easier and more accurate tuning, effectively creating a higher gear ratio.

String Tree: It doesn't seem to be necessary for each pair of strings to have the same angle, but if upward torque on the furthest point of the headstock causes problems, especially with a long 10 string, a string tree can be used to lower the strings for tension that is more parallel to the body structure.

Nut: Soft nut and saddle materials are a real killer for tone. I CNC mine in brass; as they say, it rings like a bell! Additionally, they are wider than normal with a curved approach for solid contact and a nice clean release for the string to ring true.

THE BODY

With my traditionally-influenced acoustic aesthetic inclination, I wanted a narrower Weissenborn style neck rather than the blocky steels of the 50s, but needed to be able guarantee the body forever. As mentioned at the beginning, the design process controls the final product; during this process I stumbled across a critical discovery… Our original concept was this:

We know we have to maintain that tension or everything goes poorly. If the body bends, the strings loose tension and deflect:

If the nut or saddle rotate or bend, the strings loose tension and deflect:

So what I did is trade the weight of a thicker body for the weight of two truss rods in to create a counter to the constant string tension:

The truss rods are inlaid unparalled into the lower half of the body before laminating on the top. Also note that graphite bars are inlaid into the peghead to prevent is from splitting or warping. These give great stability to a wood product that otherwise is prone to issues with changing humidity or temperature, and will never warp as it can be adjusted to perfectly flat.

Voila! No deflection, no added weight. This has made all the difference in not only the long term stability of the instrument but resulted in an instrument that is sprung like a cat, just waiting to jump, and creates a very warm near field sound for the player. It's quite cool and I am applying that discovery to electric basses and guitars.

THE TAIL

The Saddle: As previously noted, the saddle in milled from brass to match the nut tone, but is thicker to provide good contact and minimize breakage of the highest string. In addition, due to the high string tension of up to 250#, a brass stop is installed to prevent the wood grain of the bridge from crushing.

String Angle: As with the nut, downward force is necessary to maintain good contact and solid tone. Frequently one sees the strings break at close to a 90 degree angle, diving directly downward through the bridge, with no passive string length. This is a misunderstanding of force vectors; I believe that the angle and string length should roughly match the nut to provide the same ease and accuracy of tuning.

String Anchor: Strings that mount to a bracket of some sort on the top of the instrument are subject to deflection if too light, or screws loosening over time. I prefer to bring the strings through the body for maximum contact. The string ferrule wrap has to compress into a washer during the first few tunings, but after that it's bombproof.

ELECTRONICS

Pickups are very interesting and critical. The original laps used single coil pickups which have a great 50s sound, but can be quite hot and are prone to hum or other artifacts. Humbuckers were developed to counter that and are a good choice. Some builders use active pickups with a battery, but I found the tone to be too modern/electric guitar, without depth, and primarily use George L's pedal steel pickups which are nicely organic sounding. They are passive with no battery to maintain but have plenty of output, and have no moving parts to fail. Although they have been discontinued, I have enough stock to do my entire buildout with 4 different versions (10-1, SS, TW and PF) ranging from very warm Hawaiian to a crisper country sound. I also offer SteelTronics custom wound humbuckers that are close in sound to traditional single coils, but smoother and without hum or noise.

The make of the volume and tone potentiometers are more critical than you might think. I started with the most well-known guitar pots, but they were too stiff for a rapid wah-wah slide with the volume or tone control - so I switched to Bourns audio pots which are not only very smooth, but have a better frequency adjustment and are surprisingly much clearer in tone. I install a treble bleed on the volume control so that treble isn't lost as you turn down the volume (which is "normal") and a two stage tone switch between fine grained or quick adjustments.

A skinny little cord has more resistance, and if too long dampens the signal, making it darker. A thicker braided cord is always preferred.

Amp choices are complicated, with tube and solid state options, and have different settings with very different tones, effects and voices. They are a critical part of your sound.

For my legged (console) steels, I offer a leg tray with a very nice small Quilter amp head - they are as close tonally to a tube amp that you can get with terrific emulations of the Fender '57 and '65 tone. It has a speaker out to my stage monitors (which are also useful as a home speaker), and can additionally line out to a larger amp or PA for gigs. They also have line in for a backing track and headphone out. The controls are close on hand to be able to shape your sound well beyond the standard pickup tone control.

The final link of the chain is what you actually hear - the speaker itself. I am building a series of small monitors, dovetailed in mango to match the No Ka ‘Oi and sized to carry onto a plane. I will compare 10" and 12" speakers from Eminence and Celestion side by side with professional players in a variety of genres, and post those findings in the next article, which will conclude with some professional player thoughts on Finding Your Tone.

All the components in the signal chain contribute to your final tonal output, and should be carefully chosen to create the sound you want.

In the meanwhile, Mele Kalikimaka and Hau‘oli Makahiki Hou!